DE2243866A1 - DIAPHRAGMS FOR ELECTROLYTIC CELLS - Google Patents

Description

Dr. Michael Hann H / C (489)

"Β _β September 1972

Patent attorney 63 Gießen Ludwigstrasse 67

.PPG Industries, Inc., Pittsburgh, USA

DIAPHRAGMS FOR ELECTROLYTIC CELLS

Priority ι September 9, 1971 / USA / Ser.No. 179,151

According to a well-known process, alkali chlorides are used for the production of chlorine and alkali hydroxide electrolyzed in a diaphragm cell. Such electrolytic cells essentially have one Structure as described in U.S. Patents 3,337,443 and 3,022,244.

In such cells, the diaphragm serves to separate the anode compartment from the cathode compartment. As a starting material an aqueous solution of an alkali chloride, i.e. a brine, is introduced into the anode compartment. In the anode compartment is formed from the halogen ion of the dissociated alkali halide, the free halogen at the anode. The alkali ion, the hydroxyl ion and part of the halide ion migrate through the diaphragm into the cathode compartment, in which In the cathode compartment, alkali metal hydroxide and gaseous hydrogen are released at the cathode.

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The diaphragm is used, among other things, to establish a pH difference maintain between the two rooms. In the Rögel, the electrolyte has an anode space pH from about 3.5 to about 5.5, whereas in the cathode compartment its pH is 2.0 or even higher. With a typical In an electrolytic cell of the type described above, the diaphragm is used to maintain this pH difference.

As a rule, such diaphragms are made from asbestos. In the known electrolytic cells, a type of asbestos known in the literature as chrysotile is used. Chrysotile asbestos has a fibrous structure and is characterized by the empirical formula 3MgO.2SiO ₃ .2H ₂ O.

Asbestos diaphragms are generally about 3.2 mm thick when assembled and "swell" up to about 100% a thickness of about 6.4 mm in use.

Such asbestos diaphragms have electrolytic cells with graphite anodes generally a life of about 4 to about 7 months. In electrolytic cells where the anodes are dimensionally stable (i.e. the anodes have a metal substrate with an electrically conductive metal or an electrically conductive metal compound on its surface), the life of the diaphragm lies usually from about 3 to about 7 months. These diaphragm usage times are short compared to one 18 months of use, typical of the dimensionally stable Anodes is. For this reason, during the

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Period of use of such anodes several renewals of the Asbestos diaphragms are carried out. :%

It has now been found that diaphragms containing a hydrophilic, contain cation-selective poly (fluorocarbon) copolymers and are easily wetted by the sols, for the Electrolysis of alkali chloride in diaphragm cells are very suitable, especially when such cells have dimensionally stable anodes *

Such diaphragms are characterized by a long service life in electrolytic chlorine cells as they are essentially to chlorine and the other components of the medium are inert, so that their service life is only due to the mechanical abrasion from the electrolyte and the developed Gases is limited.

To keep up? a sufficient pH gradient between the anolyte and the catholyte it is sufficient if these diapnragmas have a thickness of about .0254 to about 6.35 mm. This allows <■ ·. bstand (interelectrode gap) between the anode and the cathode in electrolytic diaphragm cells. One can consequently, a greater number of electrodes for a given unit volume of electrolytic cell arrange ", so that thereby a more powerful electrolytic Cell can be built "

Another advantage of the new diaphragm after the invention is that there is a voltage drop that is up to 0.3 volts lower than that of conventional asbestos diaphragms

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• causes, so that also thereby the costs for the electrolysis products can be lowered.

The diaphragms according to the invention are suitable for alkali chloride cells to separate the anolyte with a pH of about 3.5 to about 5.5 from the catholyte with a pH of 12 or ' greater. Such cells have as typical components an anode, a cathode, a diaphragm to separate the Anolyte from the catholyte and means for applying an electromotive force between the anode and the cathode. In the diaphragms according to the invention with a thickness of about 0.0254 to about 6.35 mm and a voltage drop of less than about 0.6 volts at a current density of 20.2 amps / 100-cm (190 amperes per square foot) will result in one interelectrode gap {i.e. a distance between one Cathode and the closest anode in the cell) of less than

, about .6.35mm.

* · ■. ■ ■ ■ ■ ■

The diaphragm according to the invention is an electrolyte-permeable, hydrpphiles, cation-selective part that essentially is inert to the electrolyte. Under "hydrophilic" it is understood here that the diaphragm is light; through the Electrolyte is wetted »Under" cation-selective "wltrd vet * stood that the diaphragm preferred according to the invention the migration of cations such as Na and H through the diaphragm permitted. "Inert" is understood to mean that the diaphragm essentially through the electrolyte and the electrolysis products, like chlorine, is not attacked. According to the invention, these properties of cation selectivity, wettability and inertness is achieved by a copolymer containing fluorocarbon and acidic fluorocarbon units.

^ holds,

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The for the production of the diaphragm according to the Er = Finding particularly suitable copolymers correspond to the empirical formula

in which m is 0 to 10, the ratio of M to M is sufficient to give an equivalent weight of 800 to 2,000, which will be explained in more detail later, and R is selected from the following group:, '

A; CF ₂ Y where ρ 1 to 3 is; 4 O - CF ₂ - where p.1 to 3 is and · 4 O CF _Ä - • Ir
Y YF or CF ₃ 1st c Ό ) "· - CF ₂ - CF- * AI where ρ 1 to 4 O - CF ₂ - Y 3 is, Y -F or -CF ₃ and R _£ -F or Perfluoroalkyl rest with 1 to 10 carbon ; ■ atoms is;

- 0 A. where 0 is the aryl radical;

and - (CF ·> A where ρ is 1 to 3 ;.

and where A is an acidic group from the following groups:

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-CF ₉ SO ₃ H;

-CCl ₉ SO ₃ H;

-0 SO ₃ H; where 0 is the aryl radical;

-PO ₃ H ₂ ;

-COOH;

and 0011, where 0 is the aryl radical.

The fluorocarbon unit (CF ₀ ) is a fluorinated one

m 2m

Olefin such as tetrafluoroethylene, hexafluoropropylene, octafluorobutylene and other CF homologues from this series. However, fluorocarbon units can also be present in the mixed polymer be present whose precursors are fluorinated acetylenes, such as difluoroacetylenes, or fluorinated diolefins, such as "hexafluorobutacin, were. Derarcifra Fl-aoracetylene and Fluorodiolefins can be used as cross-linking for the fluoroolefins act, whereby the diaper a jtr.a according to the invention gain additional physical strength. In addition, small amounts of (chlorine, fluorine) hydrocarbons, v; ie monochloro trifiuoroethylene, dichlorodifluoroethylene and the like can be present without causing adverse effects.

The acidic unit (C AF _ _Ί ) is a fluoroolefinic acid,

m 2m-1 '

like the trifluoroethylene acids, the pentafluoroprop3''lenic acids, the heptafluorobutylenic acids and other Ho;.; ologe Jiooor series. The acidic group attached to this group. Λ i ..,. eiiio cation-selective ion-exchanging acid Gruv _ ■ - :. .ie the group of sulfones. 'urc (-SO-II) Fiuor- ^ '- /., L-,.,; Lfon ^ iuro (-CF, ^ O. [[),!>,., .Bu l £ oni;: tur'_ (- {' ^ Ο ,, ΙΙ '»

3 0 9 8 11/114?

ÖAD ORIGINAL

■ ■■ ■ '- 7 - - .. = · ■■.

Carboxylic acid (-COOH), phosphonic acid (-PO ₃ H ₂ ), phosphonic acid (-PO ₂ H ₂ ) or a phenol group. The symbol 0 refers to an aryl radical of the formula -GH, -. Preferred fluorocarbon acids are trifluorovinyl acids and branched trifluoroethylenes with terminal acidic groups in side chains, but other fluorocarbon acids can also be used with entirely satisfactory results.

Preferred acidic groups are sulfonic acid groups, including the sulfonic acid group (-0SO-H), the fluoromethylene sulfonic acid group (-GF ₂ SO ₃ H) and the sulfonic acid group (-SO ₃ H), since they have the greatest cation selectivity. The sulfonic acid group (-SO ₃ H) is the preferred sulfonic group. However, all of the other groups listed can be used with entirely satisfactory results.

If the fluorocarbon has short side chains, such as e.g. for poly (perfluoroethylene-trifluorovinylsulfonic acid) and as with branched polymers

and for similar polymers of this type with short side chains with terminal acidic groups, the ratio is the M to the N units, i.e. the ratio of the fluorocarbon moles to the acidic fluorocarbon moles as a rule above about 8, resulting in an equivalent weight of about 1,000 grams per MpI of acid gives * ■ In the case of such-polymers with short side chains is the ver. ratio of M to N about 5 to about 20 and bevos-gugt. approximately up to about 14j when the ratio of fluorocarbon moles to acidic fluorocarbon molea is below about 1, the mixed polymer has a low physical strength and is therefore particularly sensitive!

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22A3866

rubbed through the evolved gases and the moving electrolyte. When the ratio of fluorocarbon moles to the acidic fluorocarbon moles higher than about 20, the hydrophobic properties of the fluorocarbon moiety begin to predominate in the interpolymer. However, when ρ is large, R ^ is a perfluoroalkyl radical, i.e., that the side chain has a high molecular weight, the ratio of M to N can be less than 5 and even 1 or 0 and the equivalent weight remains in the range of 1,000.

The copolymers preferred for making the diaphragms From fluorocarbon and acidic fluorocarbon fineness are also characterized in that the fluorocarbon polymer is essentially free of carbon-hydrogen bonds. With such In polymers, the ratio of carbon-fluorine bonds to carbon-hydrogen bonds is higher than 100 to 1 and preferably higher than 400 to 1, these measurements being by nuclear magnetic resonance or by infrared spectroscopy be performed. Further characteristics of the preferred copolymers of fluorocarbon units and acidic fluorocarbon units are an equivalent weight of about 800 to about 3,000 grams each Moles of acid and a molecular weight of from about 10,000 to about 50,000,000 as determined by viscosity measurements.

Suitable for the production of the electrolyte-resistant surface, but which can easily be wetted by the electrolyte are copolymers of ethylenically unsaturated fluorocarbon compounds and ethylenically unsaturated

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Fluorocarbon acids. Such copolymers can be prepared by the process of NO-PS 3,041,317 with subsequent Hydrolysis of the sulfonyl fluoride groups to form sulfonic acid groups getting produced; also according to US Pat. No. 3,624,053. Alternatively, the copolymers can be derived from fluorocarbon, Derive material vinyl ethers, as described in US Pat. No. 3,282,875; in GB-PS 1 · 034 197 and in DT-OS 1 806 097 is.

According to one embodiment of the invention _r e is the diaphragm, a substantially homogeneous, microporous member, or member, which was made of a mixed polymer of a fluorocarbon, and an acidic fluorocarbon.

Such an essentially homogeneous diaphragm can be a mixed polymer of an olefinically unsaturated one as the main component Fluorocarbon and an olefinically unsaturated one Contain fluorocarbon acid. Alternatively, the olefinic unsaturated fluorocarbon acid has a side chain with a terminal acid group of the type

CF ₂ - CF (O-CF ₂ -CF ₂ -SO ₃ tt>

contain.

Crosslinking agents can also be incorporated into the mixed polymer in order to obtain increased durability. Examples of olefinically unsaturated fluorocarbon compounds are: tetrafluoroethylene, hexafluoropropylene, octafluorobutylene and other CF ,, homologues of this series. Examples for olefinically unsaturated fluorocarbon acids are trifluorovinyl acid, pentafluoropropylenic acid and heptafluorobutylenic acid and other CF “homologues in this series.

'ι π Q Q 1 1 y ι 1/1

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The acidic group attached to it is a cation-selective acid, such as sulfonic acid (So ₃ H), fluoromethylene _{sulfonic acid (-CF 2} SO ₃ H), benzenesulfonic acid (-0SO ₃ H), carboxylic acid (-COOH), phosphonic acid (-PO-H ₅ ), phosphonic acid (-PO ₅ H ₅ ) or a phenol (-0H). The crosslinking agent used only optionally can either be an acetylenically unsaturated fluorocarbon, such as difluoroacetylene, or a diolefinically unsaturated fluorocarbon, such as hexafluorobutadiene. Divinylbenzene can also be used as a crosslinking agent.

Although the diaphragm in this embodiment as in is referred to as essentially homogeneous, it may contain impurities without any adverse effects enter. For example, there may be residues of leachable fibrous materials that were used for this purpose to give the diaphragm its porous character. In addition, the diaphragm 1 materials to increase the physical strength or other desired properties can be added. Close such materials e.g., poly (halocarbon) fibers, glass fibers, asbestos, and the like.

The microporous diaphragm according to this embodiment can have a porosity of about 5 to about 85%. Preferred however, the porosity is around 25 to around 40%. The porosity is called the ratio of the volume of the voids defined for the total volume of the material and the voids, this quotient being multiplied by 100 to get an indication as a percentage. The porosity

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can be determined by any known method, such as gas displacement or displacement of mercury.

In this embodiment, the pores of the microporous diaphragm have an irregular shape. The single ones

Pores have a cross-sectional area of 8 10 to about

-5 2
8 χ 10 cm. Most pores have a cross-sectional

-8-11 9

area of about 10 to about 10 cm. Such pore diameters are determined according to ASTM regulations D-2499 and E-128 and by electron microscopy. The pores of the microporous diaphragm have an average pore length that is significantly greater than the thickness of the diaphragm. The mean pore length is 10 to about 10,000 times the mean pore diameter, with mean Pore length meter from about 100 to about 1,000 times preferred are.

In this way a microporous diaphragm is obtained, which is used for the flow of the electrolyte and the various Compounds in the anolyte, such as sodium chloride and hydrochloric acid, are permeable.

The microporous diaphragm usually has a thickness of 0.0254 to about 6.35 mm, with thicknesses of about 0.0254 to about 0.51 mm being preferred.

The specific resistance of the microporous diaphragm according to the invention, which is caused by a mixed polymer of a fluorocarbon and an acidic fluorocarbon, is below about 1000 ohm-cm, preferably below 200 ohm-ctn,

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The microporous diaphragm of this embodiment is for use between the anode and the cathode provided in an electrolytic cell, such as those used for the production of halogens and alkali hydroxides, such as Chlorine and caustic soda, is used. The diaphragm can be mechanically connected to an electrolyte-permeable cathode be connected, wherein it is either in contact with an electrolyte-permeable anode or at a distance therefrom Anode is arranged. Alternatively, the microporous diaphragm according to the invention can be between an electrolyte-permeable cathode and an electrolyte-permeable Anode be pressed in, the anode and the cathode as well as the acidic anolyte and the basic anolyte from each other are separated.

According to another embodiment of the invention, the cation-selective hydrophilic sol-wettable copolymers of fluorocarbon and acidic fluorocarbon can be used be a fibrous web. Such a fibrous one Network, which can have a porosity of about 15 to about 85%, can consist essentially entirely of the Mixed polymers exist. In view of the high costs of the copolymers, diaphragms are an alternative Consider that from about 0.05 to about 99.99 percent by weight of a substantially inert, fibrous material such as asbestos, Poly (perfluoroethylene), coated fiberglass or the like.

According to another embodiment of the invention, the cathode with a coating of the mixed polymer of a Fluorocarbon and an acidic fluorocarbon on the Provided the surface of the electrolyte-permeable cathode

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will. Such a cathode is a cathode in the form of a fine network with the mixed polymer Fluorocarbon and fluorocarbon acid and the anolyte on one side and the catholyte on the other hand. A fine mesh is understood here to mean a metallic cathode structure, which contains more than 8 meshes per 2.54 linear cm and an opening width of less than about 1.52 mm owns. The mixed polymer can be used as a film or as a layer on the individual strands of the cathode network are present. .

In another embodiment of the invention, the diaphragm can be made from a base member or support material. and a coating of the electrolyte-resistant copolymer of fluorocarbon and fluorocarbon acid exist.

Suitable carrier materials are permeable to the electrolyte and essentially do not react with it ^ Electrolytes. "

A carrier material is used as permeable for the electrolyte which allows the passage of the electrolyte when subjected to a pressure gradient will. Such a pressure gradient is on the order of about 25.4 to about 50.8 cm water column a water permeability of from about 5 to about 50 microns of water

2
to reach 45 cm per minute per 6j.

As. Substrate that does not react with the electrolyte is called a substrate or a carrier material,

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against the chlorine formed and against 10% by weight Sodium hydroxide is stable without causing any substantial physical weakening over a period of time of more than a year, preferably more than 18 months. Such non-reactive substrates retain their persistence in chlorine cells for a period of more than 12 to 18 months.

Appropriate base members or carriers that are permeable to electrolyte can be in fiber form. If they are in fiber form, they can be woven, non-woven, or stacked Layers of woven and nonwoven materials can be used. It can also be naturally occurring Fibers, like asbestos. Alternatively, the base members or supports can also be in the form of microporous sheets own.

Suitable carrier materials are those that are stable in a medium in which chlorine is generated. Suitable such materials are synthetic polyhalides, with polyfluorocarbon compounds being the preferred polyhalogen compounds. The preferred polyhalocarbons are characterized in that they are essentially free of hydrogen bonds, examples of such preferred substances being polyperfluoroethylene, poly (hexafluoropropylene) and the like. "Substantially free of carbon-hydrogen bonds ¹¹ is understood to mean that the ratio of carbon-fluorine bonds to carbon-hydrogen bonds in the polyfluorocarbons is higher than 100 to 1 and preferably higher than AOO to 1, if this is due to nuclear magnetic resonance or infrared spectroscopy. Satisfactory results will also be determined

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achieved with glass fibers, silicone fibers and the like. The carrier material can also be asbestos. At a In another embodiment of the invention, the carrier material can also be made from rectifier metals. Rectifier metals are those metals that take on an oxidic protective layer when connected anodically will. This group of rectifier metals includes titanium, tantalum, niobium, hafnium, tungsten, aluminum, Zircon and alloys thereof. Alternatively, the carrier or the substrate can also be another metal, such as e.g. Iron, steel, nickel, aluminum and the like, if you carefully guard against contact with the materials Electrolytes by coating with a poly (fluorocarbon) or other electrolyte-resistant material protects. ,

In the embodiment in which the substrate or base material is a poly (halocarbon), the substrate can be poly (perfluoroethylene), poly (trifluoroethylene), poly (vinylidene fluoride), poly (vinyl fluoride), poly (chlorotrifluoroethylene), poly (dichlorodifluoroethylene) , Copolymers of the monomers mentioned and the like. The preferred poly (halocarbons). are those that are essentially free of carbon-hydrogen bonds. Usually poly (perfluoroethylene) is used, which is also known as poly (tetrafluoroethylene). When reference is made here to poly (perfluoroethylene), this means that it can be replaced by other poly (fluorocarbons) which are essentially free of carbon-hydrogen bonds. The poly (perfluoroethylene) suitable for making the fibrous substrate of the diaphragm according to this invention has the empirical formula:

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In the embodiment of the invention in which the substrate is fibrous, the substrate has an air permeability of about 4 to about 60 cubic feet per square foot per minute, when determined by ASTM D-737-69 at a pressure of IA.7 psi. According to ASTM method D-570-63 it has a water absorption of about 16 to about 20%.

The porosity of the fibrous substrate is around 15 to about 85%, and preferably about 25 to about 70%. Fibrous substrates with a low porosity, e.g. with a porosity of only 5% can be used, with a slightly higher voltage drop across the Diaphragm enters.

Depending on the porosity, a typical substrate of this invention will weigh 510 grams per 6.45 cm

2 at a thickness of 0.102 cm to about 1200 grams per 6.45 cm at a thickness of 0.318 cm (18 ounces per square inch at a thickness of 0.040 inch to about 41 ounces per square inch nt a thickness of 0.125 inch).

The coating of the individual surfaces of the electrolyte ■ permeable, fibrous diaphragm has the following properties: chemical resistance to the anolyte, 'physical strength, wettability by the brine and a selectivity: for the permeability of sodium and hydroxyl ions bud. simultaneous blocking effect for dip Permeability of chloride ions through the diaphragm. In this embodiment of the diaphragm according to the invention the coatings or coatings consist of cation-active ion exchange resins, the mixed polymers of olefinic

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unsaturated fluorocarbons and olefinically unsaturated Are fluorocarbon acids.

Such fluorocarbon polymers are because of their long life in a medium in which chlorine is generated is preferred. These polymers should essentially be free of carbon-hydrogen bonds and this is understood to mean that in the polymers the ratio of carbon compounds to carbon-water Fabric bonds are higher than 100 to 1 and preferably higher than 400 to 1.

The preferred olefinically unsaturated fluorocarbons from which these polymers are derived are tetrafluoroethylene, hexafluoropropylene, octafluorobutylene and their homologues. The preferred olefinically-unsaturated fluorocarbon acids are Trifluoräthylensäuren, Hexafluorpropylensäuren, Octafluorbutylensäuren, their homologues and delayed \? Eigte Trifluoräthylenverbindungen _t having terminal acid groups in the side chains, wherein the acidic groups of sulfonic acid (-SO ₃ H), Fluormethylensulfonsäure (CF SO ₃ H) , Benzenesulfonic acid (-0SO_H), carboxylic acid (-COOH), phosphonic acid (-PO ₃ H ₂ ), phosphonic acid (-PO ₃ H ₂ ) and phenol (-0H).

In one embodiment of the invention, the coating of the ion exchange resin on the poly (perfluoroethylene) fibers consists of a copolymer of perfluoroethylene and trifluoroethylene sulfonic acid [CF ₃ = CF (SO ₃ H) J where 6 to 14 moles of perfluoroethylene per mole of trifluoroethylene

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sulfonic acid are present. In another embodiment of the invention, the ion exchange resin used for coating the poly (perfluoroethylene) is a copolymer of perfluoroethylene and CF ₂ = CF (-0-CF ₂ -CF ₂ -SO ₃ H)

with about 8 to 12 moles of perfluoroethylene per mole of acid available.

Particularly good results are achieved with a coating on the fiber with an ion exchange resin which the DuPont company ^{markets under the name 11} XR ". This is a mixed polymer of perfluoroethylene and a fluorinated sulfonic acid with an equivalent weight of about 700 to about 1600, preferably about 1000 to about 1300 and a molecular weight of about 50 to about 1,500,000, determined by viscosity measurements.

As a rule, the resin used for the coating corresponds to about 0.01 to 20% by weight of that impregnated with the resin, fibrous material based on the total weight of the resin and the fibrous resin. The porosity, water absorption and air permeability of the fibrous material are substantial after application of the ion exchange resin the same as before.

Such fibrous, electrolyte-permeable poly (fluorocarbon) substrates with a coating or a coating made of a cation-selective ion exchange resin, .that is resistant to the formation of chlorine are special good diaphragms for use in chlorine cells.

In addition to poly (halogen-

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carbon) substrates also include other fibrous materials used against the attack * by the electrolyte can be made permanent.

A suitable diaphragm can, for example, be made from an asbestos carrier and a mixed polymer of a fluorocarbon and a fluorocarbon acid. This mixed polymer can be dispersed in the asbestos carrier and thereby the cover individual fibers within the asbestos carrier and also the fibers on the outer surfaces of the asbestos carrier. Alternatively, however, the fluorocarbon-fluorocarbon acid copolymers on the outer surface of the asbestos body between the asbestos body and the. Anolytes be concentrated.

If the diaphragm is an asbestos carrier with a coating of the fluorocarbon-fluorocarbon acid copolymers is on the outer surfaces. satisfactory results with very small amounts of the resin achieved, e.g. with only 0.1 gram of the mixed polymer per

2
929 cm of the area of the diaphragm.

When using an asbestos carrier for the production of the diaphragm according to the invention, the same fluorocarbon Fluorocarbon acid copolymers are used, as already mentioned. The mixed polymer of perfluoroethylene and trifluoroethylene sulfonic acid is typical of such copolymers for coating or coating of the asbestos carrier. Another typical example is the mixed polymer of perfluoroethylene and

■ f CF ₂ = CF (O _{-CF 2} -CF _{2 -SO 3} H) ·>;

furthermore, other poly (fluorocarbons) can also be used \ nthat will be found at. they contain pendant acidic groups

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and are essentially free of carbon-hydrogen bonds.

Chrysotile asbestos is used as the carrier material for such diaphragms. This asbestos has the empirical formula

3MgO. _{2 2}

Alternatively, other forms of asbestos, such as anthophyllite or crocidolite, can also be used with good result will.

The one for the production of the diaphragms according to this type of training Asbestos used in the invention typically has a fiber length of about 0.079 to about 3.81 cm and a fiber diameter of from about 1/10 to about 20 microns.

A particularly effective type of diaphragm according to the invention is obtained by using a firmly adhering Protective film or coating of these polymers on the surface of the asbestos diaphragm facing the anolyte generated. A particularly good adhesion is achieved by having a chemical reaction between the acidic Groups of the polymer and the asbestos brings about, especially with the magnesium of the asbestos. This creates when touching the acidic polymer and asbestos, a thin (probably essentially monomolecular) firmly adhering coating of the polymer on the asbestos fibers. One way of training To obtain such a coating consists in placing a solution of the resin on the AsI) GSt under such Conditions so as not to interfere with the reaction between the polymer and the asbestos; he follows. One can

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with dispersed asbestos fibers or with asbestos as part of the diaphragm work. If you want to get the best results with the resin, you should e.g. Asbestos diaphragms taken from Zellfluigke.it are first dried and then washed with water to remove the Sodium chloride crystals are washed before the coating is applied.

Although it is not intended that the invention depend on the correctness of this theory, it is believed that the firm adherence of the polymer to the asbestos is due to the reaction of some of the polymer with the magnesium of the asbestos. The acidic group of the polymer probably reacts with the magnesium of the asbestos. The resulting reaction product seems to produce the particular stability under the reaction conditions of the electrolytic cell, this reaction product being a complex polymer containing organic components from the acidic mixed polymer and inorganic components from asbestos. This complex polymer can also be referred to as complex polymeric asbestos silicate. The reaction product between the resin and the asbestos is characterized, among other things, by its insolubility in the cell fluid _; aqueous sodium hydroxide solution, aqueous sodium chloride, ethanol, ethylene »glycol, acetone and similar solvents from»

In an alternative embodiment of the invention, a microporous or poromeric poly (fluorocarbon) substrate used as a diaphragm with a cation-selective hydrophilic agent on the inner walls of the pores »

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The preferred microporous or poromeric substrate has usually in the form of a sheet about 0.0025 to about 0.635 cm thick. Such microporous substrates typically have a porosity of from about 15 to about 85%, and preferably from about 25 to about 40%. The individual pores

τι 9 usually have a surface of about 8 χ 10 " ^iJ cm"

-5 2
up to about 8 χ 10 cm per pore, measured according to the ASTM

Methods D 2499 and E 128.

The diaphragm used in this form of training with an electrolyte-permeable microporous poly (fluorocarbon) sheet is made hydrophilic by the presence of a hydrophilic agent within the pores. Included there is no need for the hydrophilic agent to be present in all pores and on all surfaces of the pores is. Rather, the results will be satisfactory obtained even if only a small part of the pores and surfaces are made hydrophilic. Usually is a The effective proportion of pores and surfaces is achieved when the diaphragm is wetted with free water Eye can be observed. As a rule, this is the case when using the ion exchange resins already mentioned about 0.001 to about 0.01% based on the microporous sheet and resin is incorporated into the microporous sheet have been. Particularly good results are obtained when the percentage of said resin is higher than 0.01 weight percent based on the weight of the microporous sheet and resin.

In this embodiment of the invention with a microporous or poromeric sheet as a support or substrate the same ion exchange resins can be used,

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as with the use of a fibrous substrate. As already stated, the preferred ion exchange resins are polyfluorocarbons with pendant cation exchange groups. Suitable cation-selective exchange groups include the following acidic groups: sulfonic acid (-SO ₃ H), fluoromethylene _{sulfonic acid (-CF 7} SO ₃ H), benzenesulfonic acid (-0SO ₃ H) ₁ , carboxylic acid (-COOH), phosphonic acid (-PO H), phosphonous Acid (-PO Hj and phenol (-0H). The preferred acidic group is the sulfonic acid group (-SO_H).

A mixed polymer of a fluorocarbon and an acidic fluorocarbon or e5.ner fluorocarbon acid "Examples of the ion exchange resin is usually of such cation-selective ion exchange resins are the copolymers of perfluoroethylene and Trifluoräthylensulfonsäure [_ CF = CF (SO ₃ H) J, the copolymer of perfluoroethylene and [^ CF ₂ = CF (O-CF ₂ -CF ₂ -SO ₃ H)].

As already stated, such a copolymer is commercially available.

The diaphragm of the invention having an electrolyte permeable member or member and through the electrolyte is wettable and contains a fluorocarbon-fluorocarbon acid copolymer, according to various Process are produced.

According to one embodiment of the invention, a microporous part is produced, the main component of which is the mixed polymer of fluorocarbon and fluorocarbon acid. Such a microporous part can be manufactured by using the fluorocarbon and the fluoride of the fluorocarbon on-

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chemical acid according to the teaching of US Pat. No. 3,041,317 in the presence of a low-boiling solvent or a polymerized easily-leachable component and then hydrolyzed the fluoride of the acid.

In another embodiment of the invention, a solution of the mixed polymer is applied directly to the mesh-shaped cathode, a uniform cathode structure being produced. With this form of construction, one can _> cover a screen made of steel wire mesh on one side with the mixed polymer. The mesh screen, which preferably has more than 8 meshes per 2.54 cm with a mesh opening of less than 0.15 cm, is cleaned and degreased before the mixed polymer is applied. Then a solution of the mixed polymer "■ · '<" fluorocarbon and fluorocarbon acid is prepared in a solvent. The solution is on the Maschenschi t * * .a oekannter way, z. B. with brushes, rollers or by spraying. The coating would then be converted into a soft shape, for example by treatment with a caustic soda solution. In this way, an electrolyte-permeable cathode-diaphragm structure is produced, which consists of a cathode made of a wire mesh screen and an electrolyte-resistant screen the electrolyte-wettable coating on one side of this screen.

In another embodiment of the invention, a fibrous diaphragm made by mixing the fibrous substrate with a solution of the ion exchanger

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or mixed polymers of fluorocarbon and fluorocarbon acid coated, with a suitable organic Solvent is used and the impregnated fibrous substrate, e.g. B. a poly (fluorocarbon) with the cathode is then connected to form a structural unit.

Another way of making the diaphragm according to the invention is that a sheet is made from fibrous poly (fluorocarbon) with a solution a suitable ion exchange resin impregnated by placing the sheet in a solution of the ion exchange resin immersed in an organic medium. The solution is heated and then an appropriate compound is added, to convert the dissolved resin into an insoluble form.

The solution used for applying the ion exchange resin usually contains 0.1 to about 20% by weight of the resin in an organic solvent. The organic liquid used as the solvent should essentially not react with the ion exchange resin. Solvents in which the ion exchange resin has significant solubility are of interest. The preferred organic solvents are those containing two to six carbon atoms and aldehyde, ketone, or alcohol groups. Examples of preferred organic solvents are ethyl alcohol, butanol, propanol, isopropanol and the like. Alternatively you can

30981 1 / 1U?

aromatic solvents such as benzene, toluene, cumene, Phenol and the like can be used. Other alternative solvents are dimethylformamide, dimethyl acetamide, Dimethyl sulfoxide and tetramethyl urea. In one embodiment, a solution of the ion exchange resin is used s prepared in the solvent «This solution of the ion exchange resin is used, to carefully wet and penetrate the fibrous sheet. This impregnation of the fibrous sheet can be in a period of about 0.1 to about 8 hours at a temperature between freezing point and the Take place at the boiling point of the solution. Preferred times are about 1 hour to about 4 hours at the reflux temperature the solution.

The ion exchange resin is more soluble in the solution Form before, d. H. as acid. The solution of the resin and the solvent are then combined with a compound of the general formula NaX, where X is an acid residue or OH.

Usually sodium hydroxide is used for this purpose. The poly (fluorocarbon) substrate impregnated and coated with the ion exchange resin is then removed from the solution and connected to the perforated metal cathodes.

30981 1/1 U?

Electrolysis can then be carried out with such composite bodies made of metal cathodes and the diaphragm according to the invention can be carried out with good results. At the beginning, the voltage drop across the diaphragm is 2 volts and after a short period of operation, e.g. B. after about 5 days, the voltage drop across the diaphragm is less than 0.8 volts and usually less than 0.6 volts at a current density of 20.2 amps / 100 cm ^ (190 amperes per square foot).

According to another procedure, the diaphragm according to the invention is made by cutting a sheet of a poromeric or microporous poly (fluorocarbon) impregnated with an ion exchange resin by the The sheet is immersed in a solution of the ion exchange resin in an organic medium. The resin is allowed to pass through percolate and penetrate the leaf. Then the solution is heated and it becomes a compound for conversion of the resin is added in an insoluble form. The solution of the ion exchange resin in the organic The solvent used in this treatment is usually a 5% by weight solution. The same solvents can be used as are already used for the treatment of a fibrous poly (fluorocarbon) substrate.

In this treatment, too, the solution penetrates and percolates the microporous substrate and wets it Inside the pores carefully. Such an Irapregnation

309811/11 /,.?

treatment is for a period of about 1 to about 24 hours at a temperature between freezing point and carried out the boiling point of the solvent.

The ion exchange resin, which is still in soluble form, is then mixed with a sodium compound such as sodium hydroxide or a sodium salt such as sodium acetate to convert the resin to an insoluble form. Then the microporous or poromeric poly (fluorocarbon) substrate coated with the ion exchange resin is made taken from the solution and connected with perforated metal cathodes. This composite body is then ready for implementation of electrolysis.

The poromeric or microporous sheet used as the substrate can be prepared by any known method such sheets can be generated. So you can z. B. the corresponding monomers in the presence of a releasable fibrous material, e.g. B. off Cellulose acetate, polymerize and then dissolve the fibrous material from the resulting sheet.

If asbestos is used as the fibrous substrate, the asbestos can be deposited on the electrolyte-permeable cathode can be drawn up by any known method and the fluorocarbon polymer is then deposited on the fibrous Part of asbestos deposited.

The preferred procedure is to slurry the asbestos in the cell fluid. The slurry can be about Contains 2 to 4% asbestos in the cell fluid. The cell fluid is an aqueous solution that is about Contains 10 to about 15 wt% sodium hydroxide and about 10 to about 15 wt% sodium chloride, making that total a solution is formed which contains about 25 to about 30% by weight of these sodium compounds.

The asbestos is then drawn onto the cathode shield, by immersing the cathode in the slurry of cell fluid and brine and a vacuum in the cathode compartment is created. The combination of the cathode and the asbestos is then allowed to dry after washing and coats them with the mixed polymer of fluorocarbon and fluorocarbon acid.

Usually the mixed polymer is made from fluorocarbon and fluorocarbon acid applied as a dilute solution in one of the solvents already mentioned. That Applying this solution to the asbestos can be done by any method, e.g. B. by spraying, brushing on, Dipping or rolling. A typical example of the ones already mentioned Copolymers is the copolymers made from perfluoroethylene and trifluorovinyl sulfonic acid. However, the other fluorocarbon copolymers can also be used, which are essentially free of hydrogen-carbon bonds and contain acidic groups pending on them. Any of the solvents in which the copolymer is soluble can serve as the solvent.

309811/114?

After applying the solution of the copolymer on the asbestos is the diaphragm with a basic solution, z. B. with dilute sodium hydroxide treated. This converts the soluble hydrogen form of the copolymer into the insoluble sodium form, whereby the insoluble copolymers are deposited on the asbestos fibers. Afterwards is the combination of cathode and diaphragm ready for electrolysis.

In another embodiment of the invention, which can be carried out with either a poromeric or a fibrous substrate, this is done with a. Ion exchange resin coated and impregnated poly (fluorocarbon) sheet on the cathode well attached and it a slurry of asbestos in brine is then made. Usually this slurry contains about 0.5 to about 20% by weight of chrysotile asbestos in a sodium chlorid-en thai brine. The slurried asbestos will applied to the anolyte side of the diaphragm. In this way one gets a strong, long one on the cathode living and firmly adhering diaphragm.

Certain physical damage to the diaphragm can occur after long periods of electrolysis. For such damage to the diaphragm, it does not matter whether the outer asbestos surface described above is used. According to a further embodiment of the invention, this damage, which on

3098 11/1 U2

physical erosion can be substantially reduced or eliminated by removing small amounts of asbestos, e.g. B. about 2 to 454 g of asbestos per 929 cnr of the cathode area per day are added to the electrolyte during the electrolysis. The asbestos added to the brine during electrolysis is preferably chrysotir asbestos. This Ghrysotylasbest typically ₉ 4 mm fiber length etwa.O to 12.7. A suitable asbestos of this type for addition to the anolyte is sold by Asbestos Corporation of America under the designation "7MO5".

To maintain the structure of the diaphragm, the asbestos can be added to the cell, for example in the form of a slurry of asbestos in the brine, together with '.'"·. The brine supplied. Typically this slurry contains about 1 to about 100 g of asbestos per liter. The best results are obtained when the asbestos content in the slurry is about 2 to about 20 g per liter. Alternatively, the asbestos can also be added through openings in the housing of the cell.

With the help of this method of operation, it is possible to remove those parts of the diaphragm that have been damaged have to renew to a large extent and to essentially regain the original effectiveness of the cell. This means that the diaphragm can be used for long periods of use of over 9 months without oil.

'J Q 9 HI T / 1 1 /, ->

The invention is further illustrated in the following examples explained in more detail:

example 1

A microporous diaphragm was made from a mixed polymer of perfluoroethylene and a perfluorinated olefin with pendant sulfonic acid groups and reinforced with poly (perfluoroethylene) fibers. The interpolymer had an equivalent weight of about 1200 grams per gram mole of the sulfonic acid group. The diaphragm was 0.076 mm thick, had a circular diameter of 12.7 cm and had a flow rate. of 16 ml per minute at a water pressure of 43 cm (17 inch head of water), from which a porosity of

-1-2 0.81 ml minute foot calculated.

The diaphragm obtained was installed in a laboratory cell with a diaphragm. The laboratory cell had an anolyte compartment with a depth of 2.54 cm and a volume of 575 ecm and a catholyte traura of a depth of 2.54 cm and a volume of 575 ecm. The anode of the cell consisted of platinum-plated titanium mesh and was separated from the diaphragm and the cathode by a 3.2 mm gasket made of polychlorobutadiene. The cathode consisted of pressed iron mesh. Appropriate devices were available for supplying the electromotive force.

3 0 9 8 11/1 U?

The electrolysis was carried out at a current density of 110 amperes per 929 cm ^ and a cell temperature of 93 ° C carried out. It was a brine, the pH of which was adjusted to 10.3 and which contained 257 g sodium chloride per liter, delivered to the cell at a rate of 6 ml per minute.

The voltage across the cell was measured with an NLS Digital Multimeter measured and the electrode potentials were measured against a silver-silver-chloride reference electrode. The total voltage drop across the cell fluid and the diaphragm was 0.50 volts. The power efficiency that as the actual yield of sodium hydroxide divided by the theoretical yield of sodium hydroxide is defined, 'was 96%. A brine pressure (head of brine) between 15 and 20 cm was maintained.

Example 2

A diaphragm was manufactured and tested in the same manner as in Example 1, except that the distance between the electrodes from 3.2 mm to 6.4 mm by installing a spacer on the cathode flange of the laboratory diaphragm cell enlarged.

At a current density of 110 amps per 929 cm? showed the cell fluid and the diaphragm have a voltage drop of 0.55 volts and a current efficiency of 90%.

11/114?

Example 3

A diaphragm was made which was formed on a fibrous poly (perfluoroethylene) substrate Coating of a perfluorinated polymer with pendant sulfonic acid groups.

Commercial products were used for the substrate and for the acidic perfluoropolymer, the latter product being the mixed polymer of perfluoroethylene and a fluorinated sulfonic acid mentioned in the description. Before the treatment with the acidic perfluoropolymer had the poly (perfluoroethylene) a sheet weight of 850 g per 0.836 m ^2, a Luftduxchlässigkeit of 1.7 m per minute and ^J mm a thickness of 1.0. The sheet was treated with a 10% strength by weight solution of the acidic perfluoropolymer in ethanol. The acidic perfluoropolymer had an equivalent weight of about 1300. The sheet was immersed in the solution of the resin in ethanol at a temperature between 27 ° and 75 ° C and thoroughly impregnated with the solution of the resin. Then the sheet was immersed in an aqueous solution of sodium hydroxide to obtain the resin in its insoluble form as a sodium salt. The sheet treated with the resin was then dried and installed in a laboratory diaphragm of the cell described in Example 1.

30981 1 / 1U?

6 ml fed per minute of a brine which was adjusted to pH 10.3 and 257 g of sodium chloride per liter contained. The cell was kept at a temperature of 90 ° C. The electrolysis was carried out at a Current density of 110 amps per 929 cm ^ carried out. After an operating time of 96 hours, a current efficiency of 30.9% was observed, with the concentration of sodium hydroxide in the catholyte 4.74% and the voltage drop across the diaphragm Was 0.50 volts.

Then 2 types of asbestos were added to the anolyte as indicated in Table I. Asbestos I (commercial product "Calidria" TM) is a chrysotile asbestos, of about 1 χ 10 ^ colloidal fibers per gram holds and in which the ratio of length to diameter of the fibers is about 200: 1. This Asbestos was in an aqueous slurry containing 85 g of Asbestos I and 257 g of sodium chloride per liter.

Asbestos II (commercial ^{product M} 7MO5 ") is a chrysotile asbestos with an average particle size of less than minus 325 meshes. Asbestos II was also used as an aqueous slurry with 85 g of asbestos and 257 g of sodium chloride per liter.

3 0 981 1/1 U?

2 ZA 3866

The current efficiency and the voltage drop can be off Table I and represent mean values

for an operating time of 48 hours. The voltage drop

Is the voltage drop across the diaphragm and the

Electrolytes. Example 4

It is based on the procedure of Example 3 Diaphragm made which has an ion exchange resin on a poly (perfluoroethylene) carrier.

For the poly (perfluoroethylene) carrier was a commercial product with a thickness of 3.2 mm, a weight of 1160 g per 0.836 m ^ and the same porosity as the carrier in Example 3 was used.

The same acidic perfluoropolymer as in Example 3 was applied using the same procedure. That The diaphragm was placed in the laboratory line of Example 1 built-in. The electrolysis was started with a brine with a pH of 10.3 and a content of 257 g of sodium chloride per liter. The current density was 110 amperes per 929 car and the time temperature was up held at 90 ° C.

30981 1/1 U?

After an operating time of 6 days, a current efficiency of 46.4%, a concentration of Sodium hydroxide solution in the brine of 5.2% by weight and a voltage drop across the cell fluid and that Diaphragm of 0.50 volts detected. Now the addition of asbestos was carried out as indicated in Table II began. The asbestos was in a slurry of the same concentration as in Example 3 added. The voltage drops and the current yields are given in Table II as mean values given for 48 hour periods. The voltage drop applies to the electrolyte and the diaphragm.

309811/1142

TABLE I.

Days Power efficiency Voltage drop NaOH found _QQ volt NaOH theor. 2 4th 30.9 0.50 6th 88 0.46 8th 84 10 89 12th 86 0.42 14th 87 16 90 0.47 18th 90 20th 90 0.47 22nd 88 24 89 26th 88 0.46 28 30th 92 32 * 0.47 34 36 38 92 0.48

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Example 5

Two microporous diaphragms were made from a perfluorinated polyolefin with pendant sulfonic acid groups and an equivalent weight of about 1200 grams per gram-mole sulfonic acid. The diaphragms were reinforced with polyperfluoroethylene fibers. The diaphragms have a thickness of mm O ₁ 25 and a water permeability of about 16 ml per minute at 17 inches of water head for a 12.7 cm diameter of the diaphragm, resulting in a porosity of about 0.81 ml min ^"1 ft" ² results.

In each experiment, the diaphragm was platinized in a laboratory cell with a perforated Titanium anode and a cathode made of wire mesh with a distance of the anode from the cathode of 1.6 mm installed. The diaphragm was placed on top of the cathode and sealed with a polychlorobutadiene seal held. The voltage drop across the diaphragm was measured using Luggin sensors, that touched the diaphragm on each side, measured. The brine fed to the cell contained 257 g Sodium chloride per liter and had a pH between 10.3 and 11. The electrolysis was carried out at about 90 ° C carried out.

'ο n in i / 1 1

41 -

Attempt a

The first diaphragm was installed and the electrolysis was carried out at a current density of 120 amperes per 929 cm2 for 7 days. The current density was then increased to 240 amps per 929 cm ² for 5 days. The current density was then increased to 330 amperes per 929 cm ² . At a current density of 120 amperes per 929 cm ² , the current yield was 93%, the concentration of the sodium hydroxide solution in the cathode product was 120 g / l and the voltage drop across the diaphragm was 0.38 volts. At a current density of 240 amperes per 929 cm ^z , the current efficiency was 94%, the concentration of the sodium hydroxide solution in the cathode product was 135 g / l and the voltage drop across the diaphragm was 0.44 volts. At a current density of 330 amperes per 929 cm ² , the current efficiency was 97%, the concentration of the alkali in the cathode product was 133 g / l, and the voltage drop across the diaphragm was 0.64 volts.

Attempt B

The second diaphragm was installed and electrolysis was started with a current density of 330 amperes per 929 cm ² . After one day the current efficiency was 98%, the concentration of the alkali in the cathode product was 143 g / l and the voltage drop across the diaphragm was 1.02 volts. After 5 days of electrolysis

3 0 9 8 1 1/1 U?

the power efficiency had dropped to 88%, but the The concentration of the alkali in the cathode product had risen to 197 g / l and the voltage drop am The diaphragm had dropped to 0.40 volts.

Example 6

It became a diaphragm with a coating of a perfluorinated polyolefin with acidic ones attached to it Groups made on an asbestos substrate. The diaphragm was used in an electrolytic cell.

First a solution of 13.2 g sodium chloride and 12.1 g sodium hydroxide per liter was prepared. To 1626 ml 22.1 g of the commercial asbestos III and 9.9 g of the commercial asbestos IV were added to this solution. asbestos III is a short-fiber chrysotile asbestos which is tested in the "Quebec Screen Test" according to the regulations of the "Quebec Asbestos Producers Association "has a rating of 0, 2, 10, 4. The range of fiber lengths is about 1.6 to 12.7 mm and the range of fiber diameters from about 0.5 to about 30 microns. Asbestos IV is a long fiber chrysotile asbestos with a "Quebec Screen Test" of 2, 8, 4, 2, a fiber length in the range from about 6.7 to 25.4 mm and a range of fiber diameters from about 0.5 to about 30 microns.

3.0 9 8 1 1/1 U?

2 ^ 3866

The slurry was aged for 3 days. Then the Asbestos on an iron mesh cathode screen from deposited in the same manner as in the previous examples. Then the cathode and the diaphragm dried in air at room temperature for 15 days.

A solution of the perfluoropolymer with pendant sulfonic acid groups from Example 1 was then prepared, those in ethanol 2% of this commercially available Contained polymers. The solution was spread on the surface of the asbestos diaphragm. The so The resulting cathode-diaphragm assembly was then dried in air at 200 ° C. for 6 hours, followed by drying allowed to cool in air. This arrangement was then built into the laboratory cell of Example 1.

The electrolysis was started with a sol ₉ which contained 257 g of sodium chloride per liter and had a pH of about 10.3 to 11.0. At the beginning the current density was 120 amperes per 929 cm ^. After 13 days the current density was increased to 190 amperes per square centimeter.

The power efficiency was initially 73%, but increased to 84% after 5 days and to 89% after 14 days. Thereafter, the efficiency of the cell remained between 85 and 90% and the concentration of the alkali in the cathode product between 125 and 130 g / l up to the 52nd day.

3 0 9 B Π / 1 Ί / «

Example 7

Two diaphragms were made for use in identical laboratory diaphragm cells. One diaphragm was made of asbestos coated with a perfluorinated polyolefin with sulfonic acid groups attached; the other diaphragm existed only made of asbestos. Both diaphragms were made from an asbestos slurry as described in Example 6 is made. The slurry was aged for 18 days, deposited on iron mesh cathodes, washed with water, by sucking water through the diaphragms and in air at 50 ° C for three hours dried. Then the one diaphragm with 12.5 g of the perfluoropolymer with sulfonic acid groups of Example 13 coated in 1% by weight solution in ethanol and then air-dried. This gave you a cathode-diaphragm assembly containing 0.53 g of the acidic perfluoropolymer on an asbestos support per 929 cm2. The second diaphragm was not treated with a resin.

The two cathode-diaphragm assemblies were installed in the laboratory cell described in Example 1. A brine was electrolyzed which contained 257 g of sodium chloride per liter at a pH of 10.3 to 11.0. The current density was 500 amperes per 929 cm ² and the electrode spacing 3.2 mm.

30981 1/1 U?

The diaphragm treated with the acidic perfluoropolymer had a cell voltage of 4.06 volts in comparison to 4.40 volts for the untreated diaphragm. After 28 hours of operation, the Resin-treated diaphragm no erosions were found, whereas the untreated diaphragm "was badly eroded.

30981 1 / 1U2

Claims (1)

Claims 1. A method for electrolyzing a brine in an electrolytic cell that has an anode, a cathode, a diaphragm for dividing the cell into an anode compartment and a cathode compartment and means arranged outside the cell for applying an electromotive force to the anode and the cathode, characterized in that a brine is supplied to the anode compartment, a Part of the electrolyte travels out of the anode compartment through a diaphragm that passes through the Electrolyte containing wettable fluorocarbon * to pass into the cathode compartment and a sends electric current from the anode to the cathode. 2. The method according to claim 1, characterized in that the fluorocarbon is a copolymer having the following empirical formula 30981 1 / 1U2 - ■ 47 -. where m is from 0 to 10, the ratio of M to N is sufficient to give an equivalent weight of 800 to 2000 and R is from the following group of is selected: A,
(0-CF ₂ -CF ₂ ) A, (O-CF-CF) A, * ι P (0-CF ₀ -CF) (0-CF ₀ -CF) A, * ■ ι Ρ * ι -0A, and 309811/114? where ρ is 1 to 3, Y is -CF ₃ or -F, R _{f is} -F or a perfluoroalkyl radical having 1 to 10 carbon atoms and 0 is the aryl radical; and where A is an acidic group from the following groups is: -SO ₃ H; -CF ₂ SO ₃ Hj -CCl ₂ SO ₃ H; -0 SO ₃ H; -COOH; 0 OH when 0 is an aryl radical. 309811 / 1U2 1. The method according to claim 2, characterized in that the fluorocarbon is a mixed polymer Perfluoroethylene and trifluoroethylene sulfonic acid is. 4. The method according to any one of claims 1 to 3 ,, thereby characterized in that the diaphragm has a microporous part. 5. The method according to claim 4, characterized in that the microporous part is a fluorocarbon, which can be wetted with the electrolyte. 6. The method according to claim 4, characterized in that the diaphragm contains an essentially inert microporous part ₉ which is coated with a coating which can be wetted by the brine _e 7. The method according to claim 1, characterized in that the diaphragm is an essentially inert one Part is coated with a fluorocarbon coating that is wettable by the brine. 8. The method according to claim 7, characterized in that the inert part is a microporous sheet. 9. The method according to claim 7, characterized in ₉ that the inert part is fibrous. 10 '. Method according to claim 9 ₉ dacteefo characterized in that the fibrous inert part 3 0 981 1/1 U2 11. The method according to claim 9, characterized in that that the fibrous inert part is a polyfluorocarbon contains. 12. The method according to "claim 1, characterized in that that the cathode is provided with a fluorocarbon coating. 13. A method for electrolyzing a brine in an electrolytic cell which has an anode, a cathode, a diaphragm for dividing the cell into an anode compartment and a cathode compartment and means for applying an electromotive force between the anode and the cathode, characterized in that, that brine is supplied to the anode compartment; causes part of the electrolyte to pass from the anode space through a diaphragm which contains a cation-selective fluorocarbon into the cathode space and
sends electric current from the anode to the cathode. 14. Electrolytic cell comprising an anode, a cathode, means for applying an electromotive force and a diaphragm between the anode compartment and the cathode compartment, characterized in that the diaphragm contains a cation-selective fluorocarbon. 15. An electrolytic cell according to claim 14, characterized in that the cation-selective fluorine coolant contains a mixed polymer of the following empirical formula: _{309fm / 1u?} in which m is from 0 to 10 , the ratio of M to N is sufficient to give an equivalent weight of 800 to 2000 and R is selected from the following group:! . (0-CF ₉ -CF) _n (O-CF ₀ -CF) A, -0A, and 30981 1/11 / ,? where ρ is 1 to 3, Y is -CF, or -F, R _{f is} -F or a perfluoroalkyl radical having 1 to 10 carbon atoms and 0 is the aryl radical; and where A is an acidic group of the following groups: i -SO ₃ H, -CCl ₂ SO ₃ Hi
-0 -COOHi and . ■ ' 0 OH ₉ when 0 is an aryl radical. 30981 UIU? 16. Electrolytic cell according to claim 15, characterized in that the fluorocarbon is a Copolymer of perfluoroethylene and trifluoroethylene sulfonic acid is. 17. Electrolytic ^ cell according to claim 14, characterized characterized in that the diaphragm contains a microporous part. 18. Electrolytic cell according to claim 17, characterized in that the microporous part is a is cation selective fluorocarbon. 19. Electrolytic cell according to claim 17, characterized in that the diaphragm is an im is an essential inert microporous part with a cation-selective coating. 20. Electrolytic cell according to claim 14, characterized in that the diaphragm is a substantially inert part with a cation-selective fluorocarbon coating. 21. Electrolytic cell according to claim 20, characterized in that the inert part is a microporous sheet. 22. Electrolytic cell according to claim 20, characterized in that the inert part is fibrous is. 3 0 9 8 11 / 1H? 23. Slectrolytic cell according to claim 22, characterized marked that the fibrous part contains asbestos. 24. Electrolytic cell according to claim 22, characterized characterized in that the fibrous part contains a polyfluorocarbon. 25. Electrolytic cell according to claim 14, characterized in that the diaphragm is a fluorocarbon coating on the cathode. 26. Electrolytic cell with an anode, a cathode, means for applying an electromotive force and a diaphragm, characterized in that that the diaphragm contains a fluorocarbon which is mixed with aqueous solutions of Sodium chloride is wettable. 27. Reaction product of chrysotile asbestos and where m is 2 to 10, the ratio of M to N is sufficient to give an equivalent weight of - to 2000 and R is selected from the following group: 30 981 1/1 IU -SO ₃ H, , SO, H ι 'P 3- (0-CF ₀ -CF) (0-CF ₀ -CF) SO, H Z ι ρ Ζ ₍ -ϊ YR _f -0SO ₃ H where ρ is 1 to 3, Y is -CF ₃ or -F, R. is -F or a perfluoroalkyl radical having 1 to 10 carbon atoms and 0 is the aryl radical. 28. Asbestos fiber with a fluorocarbon polymer bonded to its surface. 29 »Asbestos fiber according to claim 28, characterized in that that the fluorocarbon polymer has the following empirical formula: 309811 / 11A7 . - 56 - _f to a Aqulvalenzgewlcht of yield to 2000, and R is selected from the group consisting of α selected in the 1st O to 10, the ratio of M to N is sufficiently yon ISTT CO-CF ₂ -CF) _p A, Y CO-CF ₉ -CF) _n CO-CF ₉ -CF) A, Zip Zi 30981 1 / 1H? where ρ is 1 to 3, Y is -CF ₃ or -F, R _{f is} -F or a perfluoroalcyl radical having 1 to 10 carbon atoms and 0 is the aryl radical; and where A is an acidic group from the following groups -COOHf and. 0 OH when 0 is an aryl ride 11/114? 30. Asbestos fiber according to claim 29, characterized! that A is -SO ₃ H. 31. Asbestos fiber part, characterized in that on one of its surfaces is a thin adhesive coating which is a fluorocarbon polymer contains. 32. asbestos fiber part according to claim 31, characterized in that the fluorocarbon polymer has the following empirical formula; 3098 11/114? ι Ν. R. iti the m is O to 10 , the ratio of M to N is sufficient to give an equivalent weight of 800 to 2000 and R is selected from the following group lets' (O-CF -CF) A, z _t p (0-CF ₉ -CF) 40-CF ₉ -CF) A, Z ι ρ L% -0A, and . where ρ is 1 to 3, Y is -Cf ₃ or -F »ft _f -F or a perfluoroalkyl radical with 1 to 10 carbon atoms and 0 is the aryl reet; and where A is an acidic group from the following groups Is -SO ₃ Hj. -CF ₂ SO ₃ Hj -COOK} 0 OH when 0 is an aryl radical. 3 Q 9 8 1 1/1 U 2 33. Asbestos fiber according to claim 32, characterized in that A is -SO ₃ H. 34. Asbestos fiber part, which is arranged on one side of a porous metal electrode, characterized in that that the side of this part facing away from the metal electrode has a thin, adhesive coating 'Made of a fluorocarbon polymer. 35. Asbestos fiber part according to claim 34, characterized in that the fluorocarbon polymer has the following empirical formula: 3 0 9 8 1 1 / Ί U in which m is from 0 to 10, the ratio of M to N is sufficient to give an equivalent weight of up to 2000 and R is selected from the following group (0-CF ₂ -CF ₂ ) A, CO-CF ₂ -CF) _p A, Y CO-CF ₂ -CF) CO-CF ₂ -CF) A, YR, -0A, and 309811/114? 2243886 where ρ 1 to 3 1st * Y -CF ^ or -F a perfluoroalkyl radical with 1 to 10 carbon atoms and 0 is the aryl radical; ^v and where A lets an acidic group of the following groups -COOHj 0 OH ₉ when 0 is an aryl radical 3 G Q B 3 I / Ü IU ■? 36. Asbestos fiber part, characterized in that A is -SO ₃ H. 309811/114?